html/browsers/browsing-the-web/history-traversal/event-order/before-load-hash-twice.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Popstate/hashchange/load event ordering</title>

<script>
// Set these up super-early before we hit the network for the test harness, just in case.
window.eventOrder = [];
window.onhashchange = () => window.eventOrder.push("hashchange");
window.onpopstate = () => window.eventOrder.push("popstate");
window.onload = () => window.eventOrder.push("load");
</script>

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<script>
async_test(t => {
  assert_array_equals(window.eventOrder, []);

  window.addEventListener("load", t.step_func_done(() => {
    assert_array_equals(window.eventOrder, ["popstate", "popstate", "hashchange", "hashchange", "load"]);
  }));

  location.hash = "#1";
  assert_array_equals(window.eventOrder, ["popstate"]);
  location.hash = "#2";
  assert_array_equals(window.eventOrder, ["popstate", "popstate"]);
}, "when changing hash twice, before load");
</script>